The following abbreviations are herewith defined, at least some of which are referred to within the following description of the present disclosure.    3GPP 3rd-Generation Partnership Project    AGCH Access Grant Channel    ASIC Application Specific Integrated Circuit    BSS Base Station Subsystem    BSSMAP Base Station Subsystem Mobile Application Part    BSSMAP-LE BSSMAP-Location Services Extension    BTS Base Transceiver Station    CN Core Network    DSP Digital Signal Processor    EC Extended Coverage    EC-AGCH Extended Coverage Access Grant Channel    EC-GSM Extended Coverage Global System for Mobile Communications    EC-PDTCH Extended Coverage-Packet Data Traffic Channel    EC-RACH Extended Coverage-Random Access Channel    EDGE Enhanced Data rates for GSM Evolution    EGPRS Enhanced General Packet Radio Service    eMTC Enhanced Machine Type Communications    GSM Global System for Mobile Communications    GERAN GSM/EDGE Radio Access Network    GPRS General Packet Radio Service    IA Immediate Assignment    IE Information Element    IoT Internet of Things    IPA Immediate Packet Assignment    LTE Long-Term Evolution    MME Mobility Management Entity    MS Mobile Station    MTA Multilateration Timing Advance    MTC Machine Type Communications    NB-IoT Narrow Band Internet of Things    PDN Packet Data Network    PDTCH Packet Data Traffic Channel    RACH Random Access Channel    RAN Radio Access Network    RLC Radio Link Control    SGSN Serving GPRS Support Node    SMLC Serving Mobile Location Center    TA Timing Advance    TBF Temporary Block Flow    TLLI Temporary Logical Link Identifier    TS Technical Specification    TSG Technical Specification Group    UE User Equipment    UL Uplink    UMTS Universal Mobile Telephony System    WCDMA Wideband Code Division Multiple Access    WiMAX Worldwide Interoperability for Microwave Access
At the 3rd-Generation Partnership Project (3GPP) Technical Specification Group (TSG) Radio Access Network (RAN) Meeting #72, a Work Item on “Positioning Enhancements for GERAN” was approved (see RP-161260; Busan, Korea; 13-16 Jun. 2016—the contents of which are hereby incorporated herein by reference for all purposes), wherein one candidate method for realizing improved accuracy when determining the position of a mobile station (MS) is multilateration timing advance (MTA) (see RP-161034; Busan, Korea; 13-16 Jun. 2016—the contents of which are hereby incorporated herein by reference for all purposes), which relies on establishing the MS position based on timing advance (TA) values in multiple cells.
At the 3GPP TSG-RAN1 Meeting #86, a proposal based on a similar approach was made also to support positioning of Narrow Band Internet of Things (NB-IoT) mobiles (see R1-167426; Gothenburg, Sweden; 22-26 Aug. 2016—the contents of which are hereby incorporated herein by reference for all purposes).
TA is a measure of the propagation delay between a base transceiver station (BTS) and the MS, and since the speed by which radio waves travel is known, the distance between the BTS and the MS can be derived. Further, if the TA applicable to the MS is measured within multiple BTSs and the positions of these BTSs are known, the position of the MS can be derived using the measured TA values. The measurement of the TA requires that the MS synchronize to each neighbor BTS and transmit a signal time-aligned with the estimated timing of the downlink channel received from each BTS. The BTS measures the time difference between its own time reference for the downlink channel, and the timing of the received signal (transmitted by the MS). This time difference is equal to two times the propagation delay between the BTS and the MS (one propagation delay of the BTS's synchronization signal sent on the downlink channel to the MS, plus one equal propagation delay of the signal transmitted by the MS back to the BTS).
Once the set of TA values are established using a set of one or more BTSs during a given positioning procedure, the position of the MS can be derived through a so called multilateration timing advance procedure wherein the position of the MS is determined by the intersection of a set of hyperbolic curves associated with each BTS. The calculation of the position of the MS is typically carried out by a serving positioning node (i.e., serving Serving Mobile Location Center (SMLC)), which implies that all of the derived TA and associated BTS position information needs to be sent to the positioning node (i.e., the serving SMLC) that initiated the positioning procedure.
Referring to FIG. 1 (PRIOR ART) there is shown a diagram of an exemplary wireless communication network 100 used to help explain the multilateration timing advance procedure in determining a position of a mobile station 102 (MS 102). The exemplary wireless communication network 100 has several nodes which are shown and defined herein as follows:                Foreign BTS 1043: A BTS 1043 (shown as foreign BTS3 1043) associated with a BSS 1063 (shown as non-serving BSS3 1063) that uses a positioning node 1082 (shown as non-serving SMLC2 1082) that is different from a positioning node (shown as serving SMLC1 1081) which is used by the BSS 1061 (shown as serving BSS1 1061) that manages the cell serving the MS 102 when the positioning (MTA) procedure is initiated. The derived TA information (TA3 1143) and identity of the corresponding cell are relayed by the BSS 1063 (shown as non-serving BSS3 1063), the SGSN 110 (core network), and the BSS 1061 (shown as serving BSS1 1061) to the serving positioning node (shown as serving SMLC1 1081) (i.e., in this case the non-serving BSS3 1063 has no context for the MS 102). The BSS 1063 (shown as non-serving BSS3 1063) can be associated with one or more BTSs 1043 (only one shown) and a BSC 1123 (shown as non-serving BSC3 1123).        Local BTS 1042: A BTS 1042 (shown as local BTS2 1042) associated with a BSS 1062 (shown as non-serving BSS2 1062) that uses the same positioning node 1081 (shown as serving SMLC1 1081) as the BSS 1061 (shown as serving BSS1 1061) that manages the cell serving the MS 102 when the positioning (MTA) procedure is initiated. The derived TA information (TA2 1142) and identity of the corresponding cell are relayed by the BSS 1062 (shown as non-serving BSS2 1062) and the BSS 1061 (shown as serving BSS1 1061) to the serving positioning node (shown as serving SMLC1 1081) (i.e., in this case the non-serving BSS2 1062 has no context for the MS 102) (i.e., inter-BSS communications allows the non-serving BSS2 1062 to relay the derived TA information (TA2 1142) and the identity of the corresponding cell to the serving BSS1 1061). The BSS 1062 (shown as non-serving BSS2 1062) can be associated with one or more BTSs 1042 (only one shown) and a BSC 1122 (shown as non-serving BSC2 1122).        Serving BTS 1041: A BTS 1041 (shown as serving BTS1 1041) associated with a BSS 1061 (shown as serving BSS1 1061) that manages the cell serving the MS 102 when the positioning (MTA) procedure is initiated. The derived TA information (TA1 1141) and identity of the corresponding cell are sent directly by the BSS 1061 (shown as serving BSS1 1061) to the serving positioning node 1081 (shown as serving SMLC1 1081) (i.e., in this case the serving BSS1 1061 has a context for the MS 102). The BSS 1061 (shown as serving BSS1 1061) can be associated with one or more BTSs 1041 (only one shown) and a BSC 1121 (shown as serving BSC1 1121).        Serving SMLC 1081: The SMLC 1081 (shown as serving SMLC1 1081) that commands the MS 102 to perform the positioning (MTA) procedure (i.e., the SMLC 1081 sends a Radio Resource Location services Protocol (RRLP) Multilateration Timing Advance Request message to the MS 102).        Serving BSS 1061: The BSS 1061 (shown as serving BSS1 1061) associated with the serving BTS 1041 (shown as serving BTS1 1041) (i.e., the BSS 1061 that has context information for the Temporary Logical Link Identity (TLLI) corresponding to the MS 102 for which the positioning (MTA) procedure has been triggered).        Non-serving BSS 1062 and 1063: A BSS 1063 (shown as non-serving BSS3 1063) associated with a foreign BTS 1043 (shown as foreign BTS3 1043) and a BSS 1062 (shown as non-serving BSS2 1062) associated with a local BTS 1042 (shown as local BTS2 1042) (i.e., the BSSs 1062 and 1063 do not have context information for the TLLI corresponding to the MS 102 for which the positioning (MTA) procedure has been triggered).        
FIG. 1 is an illustration of an exemplary MTA procedure involving three BTSs 1041, 1042, and 1043 associated with three timing advance (TA) values 1141, 1142, 1143 for a particular MS 102. The multilateration can involve more than three BTSs 1041, 1042, and 1043 and more than three TA values 1141, 1142, 1143. FIG. 1 illustrates an exemplary wireless communication network 100 showing the basic nodes which are needed to explain the positioning (MTA) process. It should be appreciated that the exemplary wireless communication network 100 includes additional nodes which are well known in the art.
The serving SMLC 1081 may decide to use the MTA procedure upon receiving a Base Station Subsystem Mobile Application Part-Location Services Extension (BSSMAP-LE) Perform Location Request message from the serving BSS 1061 that includes the ‘BSS Multilateration Capability’ Information Element (IE). The RRLP Multilateration Timing Advance Request message sent by the serving SMLC 1081 to the MS 102 to trigger an MTA type positioning event may include cell specific assistance information to be used by the MS 102 if it selects one or more of those cells for performing the MTA procedure. The MTA procedure may be performed using one of the following methods.
Method 1: MTA—Radio Link Control (RLC) Data Block Method.
This method involves the MS 102 sending an access request on the Random Access Channel (RACH)/Extended Coverage-Random Access Channel (EC-RACH) and being assigned a single RLC data block transmission opportunity on a Packet Data Traffic Channel (PDTCH)/Extended Coverage-Packet Data Traffic Channel (EC-PDTCH). The serving BSS 1061 uses the transmitted RLC data block for deriving Timing Advance information and the content thereof for acquiring other information (e.g., TLLI) used by the serving SMLC 1081 for proceeding with the positioning estimate.
Method 2: MTA—Extended Access Burst Method.
This method involves an MS 102 sending an access request on the RACH/EC-RACH using an Access Burst and being assigned a Timing Advance value which the MS 102 then uses to send an Extended Access Burst on the RACH/EC-RACH. The serving BSS 1061 uses the Extended Access Burst for deriving Timing Advance information and for acquiring other information (e.g., Short ID) used by the serving SMLC 1081 for proceeding with the positioning estimate (see R6-160234; entitled “Extended Access Burst for TA estimation (update of R6-160205);” Source: Nokia; Reno, Nev., U.S.A.; 14-18 Nov. 2016—the contents of which are hereby incorporated herein by reference for all purposes).
Method 3: MTA—Access Burst Method.
This method involves an MS 102 sending an access request on the RACH/EC-RACH using an Access Burst with no additional transmissions performed by the MS 102. It can only be used in cells managed by the serving BSS 1061 and makes use of a cell specific Short ID (e.g., 8 bits) value provided to the MS 102 as part of the assistance information it receives from the serving SMLC 1081 in an RRLP MTA message. The serving BSS 1061 uses the access burst alone for deriving Timing Advance information used by the serving SMLC 1081 for proceeding with the positioning estimate.
When the MS 102 uses the Access Burst method in any given cell, the MS 102 needs to know whether or not its access burst has been successfully received by the serving BSS 1061, and as such the serving BSS 1061 needs to send the MS 102 some form of acknowledgement that confirms reception of the access burst without also assigning the MS 102 radio resources for an uplink Temporary Block Flow (TBF) (i.e., since no RLC Data Block needs to be transmitted using the Access Burst method).
The legacy Immediate Assignment message is used to both acknowledge BSS reception of a specific access burst on the RACH and to assign the corresponding MS radio resources for an uplink TBF and is therefore not suitable (as currently defined) for sending as an acknowledgement to an MS that has enabled PEO (Power Efficient Operation, see 3GPP Technical Specification (TS) 44.018 V14.0.0 (2016-12); Mobile radio interface layer 3 specification; GSM/EDGE Radio Resource Control (RRC) protocol (Release 14); hereinafter “3GPP TS 44.018”; the contents of 3GPP TS 44.018 are hereby incorporated herein by reference for all purposes) and is performing the MTA procedure using the Access Burst method. Similarly, the legacy Extended Coverage (EC) Immediate Assignment Type 2 message is used to both acknowledge BSS reception of a specific set of access bursts on the EC-RACH and to assign the corresponding MS radio resources for an uplink TBF and is therefore not suitable (as currently defined) for sending as an acknowledgement to an MS that has enabled EC operation (EC-GSM-IoT, see 3GPP TS 44.018) and is performing the MTA procedure using the Access Burst method.